The present invention relates generally to a device for transmitting torque in the power train of a watercraft.
German Published Patent Application No. 39 15 527 describes a torsional vibration damper for a boat gear, which includes a primary flywheel mass on the engine side, and an elastically coupled secondary part that is formed as a hub and is rigidly connected to the marine gear. The coupling allows the flywheel to twist relative to the secondary part coupled to the marine gear. Springs disposed in the flywheel and axially supported against it in the direction of the outer diameter act on sliding elements, which are supported at inclined, plane surfaces formed on the outer contour of the hub. A friction disk acting between the flywheel and the secondary part is provided for damping the vibrations. The design necessitates the torsional vibration damper having a torsion angle of less than 45xc2x0 between the flywheel and the secondary part. There is only a small resistance to the relative twisting of the flywheel and secondary part, up to contacting the limit-position damper.
In addition, an elastic shaft coupling for boat engines, which is very similar to conventional rubber roller clutches, is described in German Published Patent Application No. 43 09 745. In order to transmit torque, elastically deformable, molded articles are arranged in the spaces between the coupling flange and a hub. At the power take-off side, a power transmission element, which is rigidly coupled to the hub and the claws of which engage with recesses of the coupling flange, is disposed on the coupling flange. For this coupling, dimensioning the output-end power transmission element beyond its required strength is recommended to form a flywheel.
Torsionally elastic couplings, which are generally used for marine gears and for damping torsional vibrations, only allow a small torsion angle between the engine and the gearbox. The damping of torsional vibrations is not satisfactory for these conventional solutions. This is particularly apparent in the case of low engine speeds typical for ships, for example, in harbor maneuvers or passing through a lock. Clearly noticeable vibrations occur in the hull, as well as high levels of driving noise. In addition to the torsional vibrations caused by the drive, torsional vibrations also originate at the propeller in propeller drives for watercraft. These torsional vibrations are formed due to hydrodynamic changes in response to a ship propeller blade racing near the adjacent hull. In this instance, the smaller torque occurring at the ship propeller generates torsional vibrations, which are dependent on engine speed and known as xe2x80x9cbeating of the blade.xe2x80x9d In addition, the effect of the rudder position also contributes to the fluctuation of the torque at the power take-off.
German Published Patent Application No. 39 15 527 describes the use of hydraulically damped, dual-mass flywheels as dynamic vibration absorbers. However, such systems are considered to be too expensive.
For the shaft coupling described, for example, in German Published Patent Application No. 43 09 745, a power transmission element disposed on the power take-off side is dimensioned to have an increased mass moment of inertia.
The present invention relates to a device for transmitting torque, which is adjusted to the conditions in the power train of a watercraft, is arranged between the engine and the gearbox, is structurally separated from the coupling or clutch, and has an elastically coupled output-end flywheel mass possessing a high mass moment of inertia. This permits a large torsion angle between the drive-end and output-end flywheel masses while simultaneously providing a high degree of damping.
It is an object of the present invention to provide a device for transmitting torque in the power train of a watercraft, which damps these typical torsional vibrations in the power train.
The device of the present invention for transmitting torque in the power train of a water craft, which may be driven by an internal combustion engine, has a first flywheel mass arranged on the crankshaft of the internal combustion engine and a second flywheel mass rigidly coupled to the transmission line of the ship drive. The first and second flywheel masses are interconnected in a torsionally elastic manner. The response characteristic of the device according to the present invention can be optimally set for damping torsional vibrations, using the stiffness parameters of the elastic connection, its damping capacity, and the coupled flywheel masses. The second flywheel mass has a high mass moment of inertia and is arranged on the power take-off side of the device. Thus, a large torsion angle between the first and second flywheel masses is possible. Torsional vibrations resulting from torque fluctuations of the engine, as well as from the effect of the power take-off, are effectively damped. Vibrations and noises are already damped from the starting engine speed. The gearbox no longer rattles in almost all engine-speed ranges. Reducing the rotational irregularities subjects the entire power train to smaller mechanical loadings, thereby increasing its service life. A further advantage of the device according to the present invention is that the elimination of the need for the torsional vibration damper on the clutch disk allows the gears to be shifted more easily because of the smaller masses to be synchronized.
In addition to the high level of driving comfort and smooth shifting, less wear reduces costs.